'74 G30 Chevy Van fuel starvation

Printable View

03.30.25, 9:52 AM
DaveW

'74 G30 Chevy Van fuel starvation

My original message disappeared, so I'm reconstructing it.
---------------------------------------------------------------------------------------------------
Original post:

My '74 G30 Chevy Van tow vehicle with 2 gas tanks has been having fuel starvation symptoms (that I for a long time thought were vapor-lock) that have been getting progressively worse since May '24.

I replaced all fuel filters, relocated the fuel line away from the exhaust manifold, replaced the fuel pump, checked for line blockage, etc.

My thought was that the only thing left was the tank-selector valve which has been known to cause issues like these. So I was asking for opinions on replacement valves (only one 12V electrical connection to activate the solenoid for the auxiliary tank) that wouldn't break the bank and were reasonably reliable.
-----------------------------------------------------------
Update:

I pulled the fuel hoses from the van's tank selector valve, removed it, and tested it by blowing/sucking on the fitting that goes to the fuel pump. It appears to work fine, sealing the aux tank hose fitting w/ zero volts applied and letting air through the other. With 12V applied, the reverse is true, meaning it's likely OK.

However, in removing it, I found that the hoses were BARELY TIGHT ON THE FITTINGS, apparently letting air get sucked in and causing the starvation. That occurred because the hoses are 3/8" ID and the fittings' diameters are 5/16" with not quite 3/8" OD barbs. The "spring" clamps sealing the 3/8" ID hoses to the undersized fittings worked from installation in the late '70's until spring 2024, but the hose(s) eventually took a set and let air past the barbs. That was a very unexpected finding, since there was absolutely no sign of leakage (which I had looked for) from any of the 3 fittings.

Not that it matters, but since the issue was present on both tanks and the selector valve fittings are only ~1/4" ID, causing some vacuum on the pump side, that fitting had to be the one causing the issue. So after almost 50 years of use, when things got warm the hose to the fuel pump got just loose enough to allow air to be sucked in.

A good thing is that almost all of the selector valves for sale are exactly the same as the almost 50-YO one I took out. I ordered a new one (installed 4/5 using worm gear hose clamps), and will keep the old one as a spare.
03.30.25, 7:52 PM
Lotus7

Wait! , your 50 year old van has developed a problem? Sheesh, dump it LOL
03.30.25, 8:02 PM
DaveW

Quote:

Originally Posted by Lotus7

Wait! , your 50 year old van has developed a problem? Sheesh, dump it LOL

Nah, can't do that. I have this compulsion to keep the old stuff running. :D
03.31.25, 9:18 AM
Mark_Silverberg

Quote:

Originally Posted by DaveW

Nah, can't do that. I have this compulsion to keep the old stuff running. :D

First race I ever saw you run (Mosport Pro FF June 1982) I think you were using that van. Always happy when I see it at the track. If there was a tow vehicle HoF that thing should be in the first class of inductees.
03.31.25, 10:06 AM
E1pix

I’d been watching our Intrepid 67 by a good dozen years by then, and sure remember the van in the ‘70s!

I used to walk around doing lettering and pinstriping in the Wayback. Thinking about it now, I have a vague recollection of trying to con Dave into pinstriping the Chev at the Runoffs, or at least flaming the darned Zink. ;)
04.11.25, 6:00 PM
DaveW

Quote:

Originally Posted by Mark_Silverberg

First race I ever saw you run (Mosport Pro FF June 1982) I think you were using that van. Always happy when I see it at the track. If there was a tow vehicle HoF that thing should be in the first class of inductees.

We bought the van for $3900 in January '75. It sat in a Chevy dealer's lot for 6 months prior because the guy that ordered it never picked it up. We have towed exclusively with it since, except for when we were loaned a 2nd tow vehicle for 2 years to tow the Shrike.
04.11.25, 8:01 PM
BLS

Quote:

Originally Posted by DaveW

We bought the van for $3900 in January '75. It sat in a Chevy dealer's lot for 6 months prior because the guy that ordered it never picked it up. We have towed exclusively with it since, except for we when were loaned a 2nd tow vehicle for 2 years to tow the Shrike.

Difficult decision on who is more remarkable, you or the van :)
06.11.25, 12:51 PM
DaveW

Addendum:

Quote:

Originally Posted by DaveW

...A good thing is that almost all of the selector valves for sale are exactly the same as the almost 50-YO one I took out. I ordered a new one (installed 4/5 using worm gear hose clamps), and will keep the old one as a spare.

The new selector valve I just bought is apparently faulty. Typical Chinesium stuff.... Even though it sounds and feels like it switches tanks with 12V on, it is apparently not sealing properly internally between the 2 tanks. Even with the 12V applied (aux tank), it still was apparently drawing ~95% of the fuel from the original OE tank. :(

So I removed it and reinstalled the 50-YO valve that seemed to be working properly (except for the loose hoses) when it was last used. Hopefully that will put an end to all this effing around.